Atmospheric Chemistry of Methylcyclopentadienyl Manganese Tricarbonyl: Photolysis, Reaction with Hydroxyl Radicals and Ozone

Abstract

The atmospheric fate of MMT has been studied using laboratory smog chamber systems. MMT absorbs strongly in the UV−visible region from 210 to 400 nm with σ (333 nm) = (1.9 ± 0.2) × 10-18 cm2 molecule-1 and undergoes photolysis at a rate estimated to be (1.3 ± 0.1) × 10-2 s-1 for a typical summer day at a latitude of 40° N. Photolysis gives CO in a molar yield that is indistinguishable from 100% and an unidentified species believed to be methylcyclopentadienyl manganese dicarbonyl (MMD), which also undergoes rapid photolysis liberating additional CO. Reaction of MMT with OH and O3 proceeds rapidly with rate constants of kOH = (1.1 ± 0.3) × 10-10 and kO3 = (7.7 ± 1.9) × 10-18 cm3 molecule-1 s-1. During the day, the atmospheric loss of MMT proceeds essentially entirely via photolysis. At night reaction with O3 can be significant.